At first you should uncomment the tls stuff from your /etc/postfix/main.cf or create the not found RSA-Key file. (/etc/postfix/ssl/smtpd.key). If I interpret the last line regarding this stuff right, maybe also the cert is missing.

Beside this, run postmap /etc/postfix/virtusertable to avoid the first error. Did you edit the file your own, or did it an CP like ISPConfig for you?